This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for Funnel for Cathode Ray Tube and Cathode Ray Tube Having this Funnel earlier filed in the Korean Industrial Property Office on Apr. 2, 2001 and there duly assigned Serial No. 2001-17327.
1. Field of the Invention
The present invention relates to a cathode ray tube (CRT), and more particularly, to a funnel for a cathode ray tube, which is designed to reduce the occurrence of implosion and crack propagation.
2. Description of the Related Art
Generally, a CRT is designed to realize an image by emitting electron-beams from an electron gun and scanning a phosphor screen deposited with red (R), green (G), and blue (B) phosphors.
As the CRT takes up much space due to its full length in a direction of a tube axis when compared with flat display panels such as a plasma display, a field emission display, and a vacuum fluorescent display, a wide angle CRT having a deflection angle of electron beams of about 100xc2x0 (degrees) has been developed.
To reduce the full length, the neck and yoke portion should be disposed close to an opened end of a funnel body portion.
However, according to a series of tests, it has been noted that a compressive stress of about 17 MPa (mega-Pascal) is applied in the vicinity of a top-of-round (TOR) defining a border between the body portion and the yoke portion when the funnel is designed having a similar thickness distribution to a conventional CRT. Such compressive stress of about 17 MPa causes the funnel to we be imploded in the safety standard test. In addition, it has been farther noted that the implosion occurrence of the CRT is above 90%, the scattering amount of fragments when the CRT is imploded is above 6 kg (kilograms), and the scattering distance is above 4 m (meters).
To solve the above problems, Japanese Laid-open Patent No. 2000-251766 for Class Funnel Cathode Ray Tube, and Cathode Ray Tube Using it by Murakami Toshihide discloses a CRT including a funnel designed having a similar thickness distribution to the conventional art, but having a thickness greater than that of the conventional art.
Describing in more detail with reference to FIG. 1, the CRT disclosed in the Japanese Laid-open Patent No. 2000-251766 includes a panel 110 and a funnel 112 connected to the panel 110. The funnel 112 includes a body portion 112a having an opened end fritted to the panel 110, a neck portion 112c in which an electron gun 114 is mounted and a yoke portion 112b is defined around a border between the body portion 112a and the neck portion 112c. 
That is, the yoke portion 112b is designed having a predetermined curvature on the basis of a point located on an outer area of the funnel 112, and the body portion 112a is designed having a predetermined curvature on the basis of a point located on an inner area of the funnel 112. Namely, the border between the yoke portion 112b and the body portion 112a is defined on the TOR at which the curvatures of the yoke portion 112b and the body portion 112a become different.
The CRT further includes a frit portion 118 for attaching the panel 110 to the funnel 112, a phosphor layer 120 excited by electron beams, a shadow mask 122 for selecting the electron beams, an anode button 124, and a deflecting coil 116. The reference sign A indicates a tube axis connecting a center of the neck portion 112c to a center of the panel 110.
The thickness of the CRT is greater than the conventional CRT by 2 mm (millimeters).
However, as the thickness of the yoke portion is increased when compared with the conventional CRT, the deflection property of the deflection yoke is deteriorated, and the weight of the CRT is increased by up to 40%.
It is therefore an objective of the present invention to provide a funnel for a cathode ray tube that can prevent the deflection property of the deflection yoke from being deteriorated and that is can reduce the compressive stress in the vicinity of the TOR to reduce the occurrence of implosion as well as reduce the crack propagation speed and the scattering distance of the fragments when an implosion occurs.
It is another objective to not excessively increase the weighit of the funnel while decreasing the occurrence of implosion at the yoke and preventing the deterioration of the deflection property.
To achieve the above and other objectives, the present invention provides a funnel for a cathode ray tube, including a body portion having an opened end connected to a panel and an alignment mark formed on an outer surface of the body portion in the vicinity of the opened end; a neck portion for housing an electron gun; a yoke portion, around which a deflection yoke is mounted, the yoke portion having a first end connected to the body portion at a top-of-round (TOR) and a second end connected to the neck portion, where a convex portion having a predetermined thickness is provided on an outer portion of the body portion and/or yoke portion from a vicinity of the end of the alignment mark to a vicinity of the TOR in a direction of a tube axis.
Preferably, a distribution area of the convex portion is defined to satisfy the following condition:
Y((+)){10xcx9c50}(mm)xe2x89xa6Xxe2x89xa6TOR((+))10(mm) 
where X is the distribution area, Y is a location of the opened end, and the plus (((+))) indicates a direction from the opened end to the neck portion.
Another preferable distribution area X of the convex portion is defined by Y((+)){10xcx9c50}(mm)xe2x89xa6Xxe2x89xa6TOR.
Another preferable distribution area X of the convex portion is defined by Y((+))10(mm)xe2x89xa6Xxe2x89xa6TOR.
Further, preferably the predetermined thickness of the convex portion is greater than 1.0 mm (millimeters).
The convex portion is not provided on a portion of the body where an anode button is mounted since it is preferable that a portion of the funnel where the anode button is mounted has a depth of less than the depth of the anode button.
Preferably, the convex portion is formed in a symmetrical shape when viewed from the neck portion, and the yoke portion has a section having a circular-shape or a non-circular-shape.
According to another aspect, the present invention provides a cathode ray tube having a funnel as defined above.